The UCSD Retrovirology Laboratory is an integral part of the UCSD Pediatric ACTU and has played an important role in the success of the AIDS Clinical Trials Program in San Diego. The Specific Aims of the Retrovirology Laboratory are: (1) To apply standardized, reproducible, and quality-controlled assays of HIV infection as virologic markers in children participating in ACTG protocols; (2) To provide essential virologic data to help guide clinical investigators in determining the scientific direction of antiretroviral studies and to determine whether an infant is HIV-infected; (3) To evaluate the utility of new virologic assays for monitoring the response of children participating in antiretroviral studies; and (4) To assist in the development of novel virologic assays which can be applied to monitor patients receiving antiretroviral therapy by providing well-characterized and properly stored specimens including serum, plasma, peripheral blood mononuclear cells, and primary viral isolates. The Laboratory is fully certified to perform qualitative and quantitative HIV cultures of peripheral blood mononuclear cells and plasma and to perform p24 antigen and PCR assays. The overall objective of the UCSD Retrovirology Laboratory in this proposal is to provide virologic data that can be used to assist in the evaluation of patients participating in ACTG studies and thus, improve therapy for HIV-infected women and children.